Achieving pain control in early rheumatoid arthritis with baricitinib monotherapy or in combination with methotrexate versus methotrexate monotherapy.

OBJECTIVES: This post hoc analysis assessed speed, magnitude and maintenance of pain improvement in patients with early rheumatoid arthritis (RA) receiving baricitinib, baricitinib and methotrexate (MTX), or MTX over 1 year. Cumulative pain and quality of life benefits were also assessed. METHODS: Randomised, double-blind, phase 3 study RA-BEGIN (NCT01711359) compared baricitinib 4 mg (N=159), baricitinib 4 mg +MTX (N=215) and MTX (N=210) in patients with RA who had no or limited prior disease-modifying antirheumatic drug treatment. Pain was assessed on a 0-100 mm Visual Analogue Scale (VAS). Proportion of patients with ≥30%, ≥50% and ≥70% pain improvement from baseline; ≤20 mm and ≤10 mm on the pain VAS; and time to achieve pain improvement thresholds were assessed over 52 weeks, as were Patient Global Assessment (PtGA) and 36-Item Short Form Health Survey Physical Component Score (SF-36 PCS) outcomes. RESULTS: Baricitinib monotherapy or combination with MTX provides greater (least square mean changes (LSM) from baseline -40 mm and -43 mm, respectively) and more rapid (median 12 and 8 weeks to ≥70% improvement, respectively) pain relief than MTX alone (LSM -31 mm, median 20 weeks to ≥70% improvement) over 52 weeks. Baricitinib, alone or combination, provides 9-10 additional weeks of limited to no pain, similar gain in achievable wellness measured through PtGA, and 5-7 additional weeks with change in SF-36 PCS ≥5 vs MTX over 1 year. CONCLUSIONS: Patients treated with baricitinib reported significantly greater and more rapid pain relief, more weeks with limited to no pain, and clinically meaningful improvements in physical health than patients treated with MTX alone over 1 year.

Efficacy of baricitinib in patients with moderate-to-severe rheumatoid arthritis with 3 years of treatment: results from a long-term study.

OBJECTIVE: To evaluate the long-term efficacy of once-daily baricitinib 4 mg in patients with active RA who were either naïve to DMARDs or who had inadequate response (IR) to MTX. METHODS: Analyses of data from two completed 52-week, phase III studies, RA-BEGIN (DMARD-naïve) and RA-BEAM (MTX-IR), and one ongoing long-term extension (LTE) study (RA-BEYOND) were performed (148 total weeks). At week 52, DMARD-naïve patients treated with MTX monotherapy or baricitinib 4 mg+MTX in RA-BEGIN were switched to open-label baricitinib 4 mg monotherapy; MTX-IR patients treated with adalimumab (+MTX) in RA-BEAM were switched to open-label baricitinib 4 mg (+MTX) in the LTE. Patients who received placebo (+MTX) were switched to baricitinib 4 mg (+MTX) at week 24. Low disease activity (LDA) [Simple Disease Activity Index (SDAI) ≤11], clinical remission (SDAI ≤ 3.3), and physical functioning [Health Assessment Questionnaire Disability Index (HAQ-DI) ≤ 0.5] were assessed. Data were assessed using a non-responder imputation. RESULTS: At week 148, SDAI LDA was achieved in up to 61% of DMARD-naïve patients and 59% of MTX-IR patients initially treated with baricitinib, and SDAI remission was achieved in up to 34% of DMARD-naïve patients and 24% of MTX-IR patients; HAQ-DI ≤ 0.5 was reached in up to 48% of DMARD-naïve patients and 38% of MTX-IR patients initially treated with baricitinib. Over 148 weeks, 3.6% and 10.7% of MTX-IR patients discontinued across treatment groups due to lack of efficacy or due to adverse events, respectively; discontinuation rates were similar in the DMARD-naïve population. CONCLUSION: Treatment with baricitinib 4 mg demonstrated efficacy for up to 3 years and was well tolerated.

Mechanistic insights explain the transforming potential of the T507K substitution in the protein-tyrosine phosphatase SHP2.

The protein-tyrosine phosphatase SHP2 is an allosteric enzyme critical for cellular events downstream of growth factor receptors. Mutations in the SHP2 gene have been linked to many different types of human diseases, including developmental disorders, leukemia, and solid tumors. Unlike most SHP2-activating mutations, the T507K substitution in SHP2 is unique in that it exhibits oncogenic Ras-like transforming activity. However, the biochemical basis of how the SHP2/T507K variant elicits transformation remains unclear. By combining kinetic and biophysical methods, X-ray crystallography, and molecular modeling, as well as using cell biology approaches, here we uncovered that the T507K substitution alters both SHP2 substrate specificity and its allosteric regulatory mechanism. We found that although SHP2/T507K exists in the closed, autoinhibited conformation similar to the WT enzyme, the interactions between its N-SH2 and protein-tyrosine phosphatase domains are weakened such that SHP2/T507K possesses a higher affinity for the scaffolding protein Grb2-associated binding protein 1 (Gab1). We also discovered that the T507K substitution alters the structure of the SHP2 active site, resulting in a change in SHP2 substrate preference for Sprouty1, a known negative regulator of Ras signaling and a potential tumor suppressor. Our results suggest that SHP2/T507K's shift in substrate specificity coupled with its preferential association of SHP2/T507K with Gab1 enable the mutant SHP2 to more efficiently dephosphorylate Sprouty1 at pTyr-53. This dephosphorylation hyperactivates Ras signaling, which is likely responsible for SHP2/T507K's Ras-like transforming activity.

Evaluation of hepatitis B virus in clinical trials of baricitinib in rheumatoid arthritis.

BACKGROUND: Reactivation of hepatitis B virus (HBV) replication is a well-recognised complication in patients receiving disease-modifying anti-rheumatic drugs (DMARDs) for rheumatoid arthritis (RA). Limited data exist on HBV reactivation among patients with RA treated with janus kinase (JAK) inhibitors. The objective of the current study was to assess HBV reactivation in clinical trials of baricitinib, an oral selective JAK1 and JAK2 inhibitor in RA. METHODS: Data were integrated from four completed Phase 3 trials and one ongoing long-term extension (data up to 1 April 2017) in patients naïve to DMARDs or who had inadequate response (IR) to DMARDs including methotrexate (MTX)-IR and/or other conventional synthetic DMARD (csDMARD)-IR, or tumour necrosis factor inhibitors-IR. Within the clinical programme, baricitinib-treated patients may have received concomitant csDMARDs including MTX, or previous treatment with active comparators including MTX or adalimumab + MTX. At screening, all patients were tested for HBV surface antigen (HBsAg), core antibody (HBcAb) and surface antibody (HBsAb). Patients were excluded if they had (1) HBsAg+, (2) HBcAb+/HBsAb- (in Japan, could enrol if HBV DNA-) or (3) HBsAb+ and HBV DNA+. HBV DNA monitoring, following randomisation in the originating Phase 3 studies, was performed in Japan for patients with HBcAb+ and/or HBsAb+ at screening, and was later instituted globally for HBcAb+ patients in accordance with evolving guidance for HBV monitoring and management with immunomodulatory therapy. RESULTS: In total, 2890 patients received at least one dose of baricitinib in Phase 3 (6993 patient-years exposure). Of 215 patients with baseline serology suggestive of prior HBV infection (HbcAb+) who received a post-baseline DNA test, 32 (14.9%) were HBV DNA+ at some point following treatment initiation; 8 of 215 patients (3.7%) had a single quantifiable result (≥29 IU/mL). Of these eight patients, four met the definition of reactivation of HBV (HBV DNA level ≥100 IU/mL); baricitinib was permanently discontinued in four patients, and temporarily interrupted in two patients. No patient developed clinical evidence of hepatitis and in five of eight patients, antiviral therapy was not used. CONCLUSION: HBV reactivation can occur among RA patients treated with DMARDs, including baricitinib, with prior HBV exposure. Our data suggest that such patients should be monitored for HBV DNA during treatment and might be treated safely with the use of antiviral therapy as needed. The risk of HBV reactivation in patients with HBsAg treated with baricitinib is unknown.

Safety of baricitinib in East Asian patients with moderate-to-severe active rheumatoid arthritis: An integrated analysis from clinical trials.

AIM: We evaluated the safety of baricitinib in an East Asian (EA) patient population with moderate-to-severely active rheumatoid arthritis (RA), through an integrated sub-analysis of data from the overall baricitinib RA clinical program. METHODS: Data from EA patients who received any dose of baricitinib from five completed studies (1 Phase 2, 4 Phase 3) and an ongoing long-term extension study were pooled up to 1 September, 2016. Exposure-adjusted incidence rates (EAIR) and incidence rates (IRs), both per 100 patient-years (PY), were calculated. RESULTS: This analysis included 740 EA patients with 1294 PY of total baricitinib exposure (maximum 3.5 years). Overall, 109 patients discontinued baricitinib due to adverse events (AEs); EAIR: 8.4. No deaths were reported in this cohort. Serious AEs were reported by 125 patients (EAIR: 9.7). Serious infections were the most common serious AEs (n = 53, IR: 4.15). IR of herpes zoster infection was 6.2; the majority of events were of mild-to-moderate severity. Three cases (IR: 0.23) of tuberculosis were reported. The IRs of malignancy (excluding non-melanoma skin cancer) was 0.99 and EAIR specifically of lymphoma was 0.1. The IR of major adverse cardiovascular events was 0.26, and deep vein thrombosis was reported in four patients (EAIR: 0.3). Two cases of gastrointestinal perforations (EAIR: 0.2) were reported. CONCLUSION: Integrated data show that baricitinib is well-tolerated in EA patients with moderate-to-severely active RA in the context of demonstrated efficacy, which is generally consistent with safety results of the overall study population.

Cardiovascular Safety During Treatment With Baricitinib in Rheumatoid Arthritis.

OBJECTIVE: To assess the frequency of cardiovascular and venous thromboembolic events in clinical studies of baricitinib, an oral, selective JAK1 and JAK2 inhibitor approved in more than 50 countries for the treatment of moderately-to-severely active rheumatoid arthritis (RA). METHODS: Data were pooled from 9 RA studies. Placebo comparison up to 24 weeks included data from 6 studies. Randomized dose comparison between baricitinib doses of 2 mg and 4 mg used data from 4 studies and from the associated long-term extension study. The data analysis set designated "All-bari-RA" included all baricitinib exposures at any dose. RESULTS: Overall, 3,492 RA patients received baricitinib (7,860 patient-years of exposure). No imbalance compared to the placebo group was seen in the incidence of major adverse cardiovascular events (MACE) (incidence rates [IRs] of 0.5 per 100 patient-years for placebo and 0.8 per 100 patient-years for 4 mg baricitinib), arterial thrombotic events (ATE) (IRs of 0.5 per 100 patient-years for placebo and 0.5 per 100 patient-years for 4 mg baricitinib), or congestive heart failure (CHF) broad term (IRs of 4.3 per 100 patient-years for placebo and 2.4 per 100 patient-years for 4 mg baricitinib). Deep vein thrombosis (DVT)/pulmonary embolism (PE) were reported in 0 of 1,070 patients treated with placebo and 6 of 997 patients treated with 4 mg baricitinib during the placebo-controlled period; these events were serious in 2 of 6 patients, while all 6 had risk factors and 1 patient developed DVT/PE after discontinuation of the study drug. In the 2 mg-4 mg-extended data analysis set, IRs of DVT/PE were comparable between the doses across event types (IRs of 0.5 per 100 patient-years in those receiving 2 mg baricitinib and 0.6 per 100 patient-years in those receiving 4 mg baricitinib). In the All-bari-RA data analysis set, the rates were stable over time, with an IR of DVT/PE of 0.5 per 100 patient-years. CONCLUSION: In RA clinical trials, no association was found between baricitinib treatment and the incidence of MACE, ATE, or CHF. With regard to incidence of DVT/PE, 6 events occurred in patients treated with 4 mg baricitinib, but no cases of DVT/PE were reported in the placebo group. During longer-term evaluation, the incidence of DVT/PE was similar between the baricitinib dose groups, with consistent IR values over time, and this was similar to the rates previously reported in patients with RA.

Molecular basis of gain-of-function LEOPARD syndrome-associated SHP2 mutations.

The Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 2 (SHP2) is a critical signal transducer downstream of growth factors that promotes the activation of the RAS-ERK1/2 cascade. In its basal state, SHP2 exists in an autoinhibited closed conformation because of an intramolecular interaction between its N-SH2 and protein tyrosine phosphatase (PTP) domains. Binding to pTyr ligands present on growth factor receptors and adaptor proteins with its N-SH2 domain localizes SHP2 to its substrates and frees the active site from allosteric inhibition. Germline mutations in SHP2 are known to cause both Noonan syndrome (NS) and LEOPARD syndrome (LS), two clinically similar autosomal dominant developmental disorders. NS-associated SHP2 mutants display elevated phosphatase activity, while LS-associated SHP2 mutants exhibit reduced catalytic activity. A conundrum in how clinically similar diseases result from mutations to SHP2 that have opposite effects on this enzyme's catalytic functionality exists. Here we report a comprehensive investigation of the kinetic, structural, dynamic, and biochemical signaling properties of the wild type as well as all reported LS-associated SHP2 mutants. The results reveal that LS-causing mutations not only affect SHP2 phosphatase activity but also induce a weakening of the intramolecular interaction between the N-SH2 and PTP domains, leading to mutants that are more readily activated by competing pTyr ligands. Our data also indicate that the residual phosphatase activity associated with the LS SHP2 mutant is required for enhanced ERK1/2 activation. Consequently, catalytically impaired SHP2 mutants could display gain-of-function properties because of their ability to localize to the vicinity of substrates for longer periods of time, thereby affording the opportunity for prolonged substrate turnover and sustained RAS-ERK1/2 activation.

Phosphatase of regenerating liver 3 (PRL3) provokes a tyrosine phosphoproteome to drive prometastatic signal transduction.

Phosphatase of regenerating liver 3 (PRL3) is suspected to be a causative factor toward cellular metastasis when in excess. To date, the molecular basis for PRL3 function remains an enigma, making efforts at distilling a concerted mechanism for PRL3-mediated metastatic dissemination very difficult. We previously discovered that PRL3 expressing cells exhibit a pronounced increase in protein tyrosine phosphorylation. Here we take an unbiased mass spectrometry-based approach toward identifying the phosphoproteins exhibiting enhanced levels of tyrosine phosphorylation with a goal to define the "PRL3-mediated signaling network." Phosphoproteomic data support intracellular activation of an extensive signaling network normally governed by extracellular ligand-activated transmembrane growth factor, cytokine, and integrin receptors in the PRL3 cells. Additionally, data implicate the Src tyrosine kinase as the major intracellular kinase responsible for "hijacking" this network and provide strong evidence that aberrant Src activation is a major consequence of PRL3 overexpression. Importantly, the data support a PDGF(α/ß)-, Eph (A2/B3/B4)-, and Integrin (ß1/ß5)-receptor array as being the predominant network coordinator in the PRL3 cells, corroborating a PRL3-induced mesenchymal-state. Within this network, we find that tyrosine phosphorylation is increased on a multitude of signaling effectors responsible for Rho-family GTPase, PI3K-Akt, STAT, and ERK activation, linking observations made by the field as a whole under Src as a primary signal transducer. Our phosphoproteomic data paint the most comprehensive picture to date of how PRL3 drives prometastatic molecular events through Src activation.

Integrated analysis of global mRNA and protein expression data in HEK293 cells overexpressing PRL-1.

BACKGROUND: The protein tyrosine phosphatase PRL-1 represents a putative oncogene with wide-ranging cellular effects. Overexpression of PRL-1 can promote cell proliferation, survival, migration, invasion, and metastasis, but the underlying mechanisms by which it influences these processes remain poorly understood. METHODOLOGY: To increase our comprehension of PRL-1 mediated signaling events, we employed transcriptional profiling (DNA microarray) and proteomics (mass spectrometry) to perform a thorough characterization of the global molecular changes in gene expression that occur in response to stable PRL-1 overexpression in a relevant model system (HEK293). PRINCIPAL FINDINGS: Overexpression of PRL-1 led to several significant changes in the mRNA and protein expression profiles of HEK293 cells. The differentially expressed gene set was highly enriched in genes involved in cytoskeletal remodeling, integrin-mediated cell-matrix adhesion, and RNA recognition and splicing. In particular, members of the Rho signaling pathway and molecules that converge on this pathway were heavily influenced by PRL-1 overexpression, supporting observations from previous studies that link PRL-1 to the Rho GTPase signaling network. In addition, several genes not previously associated with PRL-1 were found to be significantly altered by its expression. Most notable among these were Filamin A, RhoGDIα, SPARC, hnRNPH2, and PRDX2. CONCLUSIONS AND SIGNIFICANCE: This systems-level approach sheds new light on the molecular networks underlying PRL-1 action and presents several novel directions for future, hypothesis-based studies.

Structural and mechanistic insights into LEOPARD syndrome-associated SHP2 mutations.

SHP2 is an allosteric phosphatase essential for growth factor-mediated Ras activation. Germ-line mutations in SHP2 cause clinically similar LEOPARD and Noonan syndromes, two of several autosomal-dominant conditions characterized by gain-of-function mutations in the Ras pathway. Interestingly, Noonan syndrome SHP2 mutants are constitutively active, whereas LEOPARD syndrome SHP2 mutants exhibit reduced phosphatase activity. How do catalytically impaired LEOPARD syndrome mutants engender gain-of-function phenotypes? Our study reveals that LEOPARD syndrome mutations weaken the intramolecular interaction between the N-SH2 and phosphatase domains, leading to a change in SHP2 molecular switching mechanism. Consequently, LEOPARD syndrome SHP2 mutants bind upstream activators preferentially and are hypersensitive to growth factor stimulation. They also stay longer with scaffolding adapters, thus prolonging substrate turnover, which compensates for the reduced phosphatase activity. The study provides a solid framework for understanding how individual SHP2 mutations cause diseases.

PRL-1 protein promotes ERK1/2 and RhoA protein activation through a non-canonical interaction with the Src homology 3 domain of p115 Rho GTPase-activating protein.

Phosphatases of the regenerating liver (PRL) play oncogenic roles in cancer development and metastasis. Although previous studies indicate that PRL-1 promotes cell growth and migration by activating both the ERK1/2 and RhoA pathways, the mechanism by which it activates these signaling events remains unclear. We have identified a PRL-1-binding peptide (Peptide 1) that shares high sequence identity with a conserved motif in the Src homology 3 (SH3) domain of p115 Rho GTPase-activating protein (GAP). p115 RhoGAP directly binds PRL-1 in vitro and in cells via its SH3 domain. Structural analyses of the PRL-1·Peptide 1 complex revealed a novel protein-protein interaction whereby a sequence motif within the PxxP ligand-binding site of the p115 RhoGAP SH3 domain occupies a folded groove within PRL-1. This prevents the canonical interaction between the SH3 domain of p115 RhoGAP and MEKK1 and results in activation of ERK1/2. Furthermore, PRL-1 binding activates RhoA signaling by inhibiting the catalytic activity of p115 RhoGAP. The results demonstrate that PRL-1 binding to p115 RhoGAP provides a coordinated mechanism underlying ERK1/2 and RhoA activation.

Activity-based protein profiling of protein tyrosine phosphatases.

The ability to accurately monitor the dynamics involved with the activity and state of a specific protein population in a complex biological system represents one of the major technological challenges in studying systems biology. Over the past several years a number of groups have attempted to spearhead this new frontier of systems biology by developing enzyme family-specific activity-based chemical probes linked to appropriate reporter groups that by nature only target and subsequently tag the active form of these enzymes. In this work, we will highlight the methods used to characterize activity-based probes as to their utility in biological contexts. Specifically, we will address activity-based protein profiling of the protein tyrosine phosphatases, a highly conserved enzyme family responsible for the phospho-tyrosine hydrolysis reaction, a ubiquitous reaction that is absolutely essential to the regulation of a myriad of cellular processes.

Seleninate in place of phosphate: irreversible inhibition of protein tyrosine phosphatases.

A homotyrosine based seleninic acid irreversibly inhibits protein tyrosine phosphatases by forming a covalent selenosulfide linkage with the active site cysteine sulfhydryl specifically. The details of the event are revealed by model synthetic studies and by kinetic, mass spectrometric, and crystallographic characterization.

Translational control of C-terminal Src kinase (Csk) expression by PRL3 phosphatase.

Phosphatase of regenerating liver 3 (PRL3) is up-regulated in cancer metastases. However, little is known of PRL3-mediated cellular signaling pathways. We previously reported that elevated PRL3 expression increases Src kinase activity, which likely contributes to the increased tumorigenesis and metastasis potential of PRL3. PRL3-induced Src activation is proposed to be indirect through down-regulation of Csk, a negative regulator of Src. Given the importance of PRL3 in tumor metastasis and the role of Csk in controlling Src activity, we addressed the mechanism by which PRL3 mediates Csk down-regulation. PRL3 is shown to exert a negative effect on Csk protein synthesis, rather than regulation of Csk mRNA levels or protein turnover. Interestingly, the preferential decrease in Csk protein synthesis is a consequence of increased eIF2 phosphorylation resulting from PRL3 expression. Reduced Csk synthesis also occurs in response to cellular stress that induces eIF2 phosphorylation, indicating that this regulatory mechanism may occur in response to a wider spectrum of cellular conditions known to direct translational control. Thus, we have uncovered a previously uncharacterized role for PRL3 in the gene-specific translational control of Csk expression.

Direct detection of glycogenin reaction products during glycogen initiation.

Glycogenin initiates glycogen synthesis in an autocatalytic reaction in which individual glucose residues are covalently linked to Tyrosine 194 in order to form a short priming chain of glucose residues that is a substrate for glycogen synthase which, combined with the branching enzyme, catalyzes the bulk synthesis of glycogen. We sought to develop a new enzymatic assay to better characterize both the chemical and enzymatic characteristics of this unusual reaction. By directly detecting the reaction products using electrospray mass spectrometry this procedure permits both the visualization of the intact individual reaction species produced as a function of time and quantitation of the levels of each of species. The quantitation of the reaction agrees well with previous measurements of both catalytic rate and the change in rate as a function of average glucosylation. The results from this assay provide new insight into the mechanism by which glycogenin catalyzes the initiation reaction.

beta-Tubulin mutations are associated with resistance to 2-methoxyestradiol in MDA-MB-435 cancer cells.

2-Methoxyestradiol is an estradiol metabolite with significant antiproliferative and antiangiogenic activity independent of estrogen receptor status. To identify a molecular basis for acquired 2-methoxyestradiol resistance, we generated a stable 2-methoxyestradiol-resistant (2ME2R) MDA-MB-435 human cancer cell line by stepwise exposure to increasing 2-methoxyestradiol concentrations. 2ME2R cells maintained in the presence of the drug and W435 cells maintained in the absence of the drug showed 32.34- to 40.07-fold resistance to 2-methoxyestradiol. Cross-resistance was observed to Vinca alkaloids, including vincristine, vinorelbine, and vinblastine (4.29- to 6.40-fold), but minimal resistance was seen to colchicine-binding agents including colchicine, colcemid, and AVE8062A (1.72- to 2.86-fold). No resistance was observed to paclitaxel and epothilone B, polymerizing agents (0.89- to 1.14-fold). Genomic sequencing identified two different heterozygous point mutations in the class I (M40) isotype of beta-tubulin at amino acids 197 (Dbeta197N) and 350 (Kbeta350N) in 2ME2R cells. Tandem mass spectrometry confirmed the presence of both wild-type and the mutant beta-tubulin in 2ME2R cells at the protein level. Consistently, treatment of parental P435 cells with 2-methoxyestradiol resulted in a dose-dependent depolymerization of microtubules, whereas 2ME2R cells remained unaffected. In contrast, paclitaxel affected both cell lines. In the absence of 2-methoxyestradiol, 2ME2R cells were characterized by an elevated level of detyrosination. Upon 2-methoxyestradiol treatment, levels of acetylated and detyrosinated tubulins decreased in P435 cells, while remaining constant in 2ME2R cells. These results, together with our structure-based modeling, show a tight correlation between the antitubulin and antiproliferative effects of 2-methoxyestradiol, consistent with acquired tubulin mutations contributing to 2-methoxyestradiol resistance.

Identification of serum N-acetylmuramoyl-l-alanine amidase as liver peptidoglycan recognition protein 2.

N-acetylmuramoyl-l-alanine amidase (NAMLAA) hydrolyzes bacterial peptidoglycan and is present in human serum. A peptidoglycan-recognition protein 2 (PGLYRP2) is expressed in human liver and has N-acetylmuramoyl-l-alanine amidase activity. Here, we determined the amino acid sequences of human serum NAMLAA and liver PGLYRP2 and tested the hypothesis that serum NAMLAA and PGLYRP2 are the same protein. Liver PGLYRP2 and serum NAMLAA had the same mass determined by mass spectrometry and polyacrylamide gel electrophoresis, and both proteins and recombinant PGLYRP2 reacted with polyclonal anti-NAMLAA and anti-PGLYRP2 antibodies, and with monoclonal anti-NAMLAA antibodies. Digestion of serum NAMLAA with trypsin, chymotrypsin, or trypsin plus V8 protease, or with CNBr yielded, respectively, 37, 40, and 3 overlapping peptides that matched 100% and covered 81% of the deduced amino acid sequence of mature PGLYRP2. These peptides overlapped all exon-intron junctions indicating no alternative splice forms. Digestion of liver PGLYRP2 with trypsin yielded 23 peptides that matched 100% and covered 44% of the deduced amino acid sequence of mature PGLYRP2. Serum NAMLAA had a C398-C404 disulfide, partial phosphorylation of S218, and deamidation of N253 and N301. These results indicate that serum NAMLAA and liver PGLYRP2 are the same protein encoded by the pglyrp2 gene.